3 Replies Latest reply on Jan 11, 2012 6:57 AM by Randy Miller

    Deciphering bolt load results

    Randy Miller

      I hope someone can help resolve my confusion regarding the list of bolt forces (see attached).  Is there some kind of picture or figure that explains what direction and magnitude is given for each load?  I've looked through the knowledge database and read a few papers on the design behind bolt connectors but nothing I could find provides explanations for the bolt load calculation results.  The pin loads are understandable but the bolt loads don't make sense to me since they have shear loads in all 3 axes (x, y and z) as well as axial and bending moments in all three axes.  Some of these loads are significant so I don't want to ignore them.  See attached for the list I'm looking at.  Any ideas?  The highlighted cells are the ones I'm interested in.  In essence I have two plates separated by a spacer and the bolts hold the plates to the spacer at each end of the spacer.  In the assembly there is loading on the pin from several members as well as loading on each of the plates. 

       

      My end game is to use these loads, obtained in an assembly study, to analyze the component part by itself with all the applicable loads derived from the assembly.  My hope is it will allow for faster solve times and allow me to improve the mesh quality.  In addition, knowing what loads are on the bolt will help me to select appropriate material.

       

      Any help is much appreciated.

        • Re: Deciphering bolt load results
          Paul Kellner

          Randy,

           

          Like anything in FEA the best way is to do a test case, a simple test case to better understand the tool before doing something complex.

           

          Just looking at your results, I would say that they are given in terms of the global coordinate system centered on the origin. But I can't confirm that just now.

            • Re: Deciphering bolt load results
              Randy Miller

              Paul, thanks for the response.  I agree with your approach.  As some additional background information, in working with my VAR and SW on this issue they threw enough doubt on bolt connectors that I won't use them until I can better understand them through the method you suggest.  Thanks again.

            • Re: Deciphering bolt load results
              Kevin Corr

              Elastic beam theory says shear will exist in any other direction than principal. From Mohr circle days(for me, 1987, rest in peace Igor Popov), the only coordinate system not having any shear is the one aligned to the principal axes. With that, one could find the principal stress direction, set up a coordinate system aligned in that sense and display the bolt loads aligned to that coordinate system.  I would hope for minimum shear values from FEA approximations of bolt loads.